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TT: Fachverband Tiefe Temperaturen

TT 9: SC: Poster Session

TT 9.22: Poster

Montag, 22. März 2010, 14:00–18:00, Poster A

Universal normal state susceptibility in iron pnictides — •Rüdiger Klingeler, Norman Leps, Christian Hess, Ulrike Stockert, Hans-Joachim Grafe, Franziska Hammerath, Guillaume Lang, Mahmoud Abdel-Hafez, Luminita Harnagea, Surjeet Singh, Sabine Wurmehl, Günter Behr, Vladislav Kataev, Igor Morozov, and Bernd Büchner — Leibniz Institute for Solid State and Materials Research (IFW) Dresden, Germany

The normal state magnetisation of iron pnctides exhibits a universal increase upon heating. In LaFeAsO_1−xF_x, both the slope and the absolute value of the susceptibility at elevated temperatures are independent on doping, irrespectively whether long range antiferromagnetic order or the non-magnetic superconducting ground state appears. Our data on LiFeAs, NaFeAs, Ba- and Ca(Fe_1−xCo_x)₂As₂ single crystals imply the generic nature of this feature. Remarkably, there is quantitative agreement of the slope well above the ground states. We present a scenario of robust local antiferromagnetic correlations persisting even in the superconducting regime of the phase diagram. In addition, we present the phase diagrams based on our specific heat, thermal expansion, µSR, magnetisation and resistivity data. In particular, our data allow to assessing the size of renormalisation effects and we discuss the particular case of LiFeAs.